Medical implant of the type of a wrap-around cuff electrode assembly

ABSTRACT

The invention is a medical implant which is a wrap-around cuff, comprising a flexible, biocompatible, film-like carrier substrate, that has a carrier substrate region which upon wrapping around a wrap axis forms a tube. The invention has a protective structure is directly or indirectly attached to the carrier substrate, which can be transformed from a first, open state into a second, closed state enclosing the carrier substrate region wrapped to form a tube at least axially around a wrap axis completely in the peripheral direction of the tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to International Application No. PCT/EP2019/071025,filed Aug. 5, 2019, which claims priority to German Patent ApplicationNo. 10 2018 213 120.1, filed Aug. 6, 2018, the contents of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to a medical implant of a wrap-around cuffelectrode assembly, cuff electrode in short, which comprises abiocompatible, film-like carrier substrate, that has the first carriersubstrate region, which by being wrapped around a wrap axis, assumes theform of a tube.

DESCRIPTION OF THE PRIOR ART

Electronic implants which are suitable for permanent or at leastlong-term placement in the body, are typically used for the therapeuticinfluencing of organ functions. Among the wide variety of implantsdifferently designed and specially assembled implants for differenttherapeutic applications, the further considerations mainly relate to animplant designed as a wrap-around electrode assembly, also known as acuff electrode, that is specially configured for intracorporealapplication and for as permanent as possible fastening along a nervefiber bundle in order at least to apply electrical stimulation signalsto the nerve fiber bundle as required.

A medical implant of this type, suitably configured in the manner of awrap-around cuff for the purpose of detection as well as application ofneuronal electrical signals for permanent or at least long-termpositioning along a nerve fiber bundle within the human or animal bodyis described in document WO 2016/055512 A1 and is also shownschematically in FIG. 2. The medical implant 1 made of a biocompatible,flat or film-like surface substrate 2 and configured as a wrap-aroundcuff, comprises a first carrier substrate region 3 which is wrappedaround a spatial axis 5 to form at least one substrate wrapping,preferably forming one and a half, two or multiple substrate wrappingswhich are radially surrounded in a straight cylindrical hollow space H.Attached on the substrate surface facing the straight cylindrical hollowspace H are electrode surfaces, not shown in FIG. 2, which come intodirect or indirect physical contact with the epineurium of a nerve fiberbundle, also not shown in FIG. 2, surrounded by the wrap-around cuff 1.In order to guarantee that on the one hand the medical implant 1 remainsas fixed in place as possible along a nerve fiber bundle aftercorresponding implantation, and on the other hand can follow the naturalchanges in shape of the nerve fiber bundle or at least does not subjectthis to any significant mechanical resistance, the individual substratewrappings adjoin each other loosely and can, in the event of expansionof the nerve fiber bundle, increase the diameter of the encompassedhollow space H through appropriate relative movement.

Through material pre-tensioning introduced into the substrate carrier 2in a first carrier substrate region 3 the surface substrate 2 takes on apredefined wrapping configuration without the effect of external forces,in which the free section end 4 is at least loosely covered by at leastone layer of the first carrier substrate region 3, that is radiallycovered by at least one surface substrate wrapping.

In this form of embodiment, adjoining the wrapped first carriersubstrate region 3 in one piece is a second carrier substrate region 6which is not wrapped around the spatial axis 5 and within whichelectrical supply and discharge leads are guided which are connected tothe electrodes which directly or indirectly come into contact with theepineurium of the nerve fiber bundle. In the shown example ofembodiment, the also flat second carrier substrate region 6 comprises aweb-like surface region 61 orientated in parallel to the spatial axis 5,which via an interface S, which is not shown in more detail and is inthe form of an implantable plug connection S, for example, is connectedto a connection structure 7 leading away from the medical implant 1,along which the electrical leads are taken to a separate, preferablyimplantable, supply unit in the form of a control device or an energysource.

In an unstressed state, the mechanical implant 1 lies along a nervefiber bundle N in accordance with the schematic view in FIG. 3auniformly enclosing in diameter the first substrate region 3 shaped intoa wrap-around cuff. In this state, no force, or only a minimalmechanical external force acts on the nerve fiber bundle N. On the otherhand, if external forces F, originating, for example, from the body'sown movements, act on the medical implant 1, deformations of thewrapping geometry can occur along the first substrate portion 3configured as a wrap-around cuff, through which the fastening of themedical implant along the nerve fiber bundle N can no longer beguaranteed, and on the other hand, a mechanical stress can act on thenerve fiber bundle through the medical implant. Such stress situationsare outlined in FIGS. 3b to e . Thus, for example, tensile forces F,which are essentially orientated in parallel to the longitudinalextension of the nerve fiber bundle N result in a funnel-shapeddeformation within the wrap-around cuff which on the one hand leads to aconstriction E on the nerve fiber bundle N, and on the other hand to awidening A, and associated radial distancing of the wrap-around cufffrom the nerve fiber bundle N as shown in FIGS. 3b and c . ConstrictionE of the nerve fiber bundle N can also occur in the case of a force F,orientated orthogonally to the longitudinal extension of the nerve fiberbundle, acting on the medical implant 1, as shown as the stresssituation illustrated in FIG. 3d . In this case the force F acts as atensile force acts transversely to the nerve fiber bundle N. In FIG. 3ethe force acts in the opposite force direction in the form of a thrustforce directed onto the nerve fiber bundle N, through which thewrap-around cuff widens in diameter and tends to become detached fromthe nerve fiber bundle N.

Cuff electrodes of the type in question implanted for the long term, arealso subject to a further disadvantageous effects which can lead tofunctional impairments and to making possibly required surgical removalof the cuff electrode from the nerve fiber more difficult and which iscaused by natural tissue growth, through which the cuff electrode welland truly becomes grown in along the nerve fiber bundle or is completelyovergrown by tissue. Because of the loose carrier substrate wrappingwithin the first carrier substrate region wrapped to form a tube,growth-related areas of tissue could also penetrate between individualsubstrate layers.

Another type of cuff electrode is described in US application2013/0123895 A1, which in contrast to a wrap-around electrode, comprisesa cuboid basic body onto which two lobe-shaped flat sections are appliedwhich, overlap each other in one layer and surround a nerve. Through themutual surrounding of both flat sections, the radially outer lying flatsection stabilises the radially inner lying flat section.

SUMMARY OF THE INVENTION

NON The invention is based on further developing a medical implant of awrap-around cuff electrode assembly, cuff electrode in short, whichcomprises a biocompatible, film-like carrier substrate, that comprises acarrier substrate region, which through being wrapped around a wrappingaxis, assumes the form of a tube, in such a way that the aforementioneddrawbacks with regard to tensile force-caused, mechanical stresses andthe wrap-around cuff deformations resulting therefrom, as well as thetissue growth-associated overgrowing of the cuff electrode and theconnected risks of injury in the case of required surgical removal ofthe implant from the nerve fiber bundle, to be significantly reduced orcompletely avoided. In addition, the invention secures the implantagainst dislocation and complete detachment from the intracorporealvessel or nerve fiber bundle.

According to the invention, a medical implant in the form of a cuffelectrode is has features being applied directly or directly on thecarrier substrate which is a protective structure that can betransferred from a first, open state into a second, closed state inwhich encloses the carrier substrate region which is wrapped into atube, at least axially to the wrapping axis in parts and completely inthe peripheral direction of the tube.

The basis of the protective structure configured in accordance with theinvention relates to a wrapping or sheathing for the cuff electrodeapplied along a nerve fiber bundle for the purpose of mechanicalprotection and additional holding of the cuff electrode, in particularfor the carrier substrate region which is wrapped to form a straightcylindrical tube and directly contacts the nerve fiber bundle. Theprotective structure is also able to form a barrier against cell atleast one of and tissue growth overgrowing the cuff electrode.

To make handling as easy as possible for the doctor, the protectivestructure according to the invention is inseparably applied eitherdirectly on the carrier substrate of the cuff electrode or directly toan electrical supply and outlet structure, which is preferablyconnectable to the cuff electrode by a detachably fixed jointconnection. In this way the doctor can apply the protective structureindirectly or directly attached to the carrier substrate immediatelyafter applying the cuff electrode around the nerve bundle in aconstructively precisely predetermined location and position in relationto the cuff electrode. Time-consuming positioning and centering of theprotective structure relative to cuff electrode is no longer necessarydue to the spatially firmly predetermined allocation between theprotective structure and cuff electrode. It is also ensured thatseparation of the protective structure from the implant is ruled out.

Preferably, the protective structure is directly or indirectly connectedby a web-like connecting section to the carrier substrate. In the caseof direct application of the protective structure to the carriersubstrate, the preferably film-like protective structure is connectedmonolithically by a web-like connecting section to the carriersubstrate.

The application, as well as the shape and size dimensioning of the atleast one connecting section, is preferably selected in such a way thatthe film-like protective structure assumes a distinct position andlocation relative to the carrier substrate section wrapped to form atube so that the doctor can clearly and securely transfer the protectivestructure from the first, open state for the purpose of surrounding orsheathing, into the second, closed state, enclosing the first substratesection wrapped to form a tube, in which the protective structure ispreferably axially and in the peripheral direction completely covers thecarrier substrate section wrapped to form a tube. Preferably the axialextent of the protective structure is larger than the cuff electrode, sothat in the closed, second state, the protective structure axiallyprojects beyond the second carrier substrate section of the cuffelectrode wound to form a tube on both sides, with an overlap in eachcase. Through this it can be reliably prevented that the cuff electrodebecomes overgrown by surrounding tissue over the course of time.

Depending on the design and form of the film-like carrier substrate ofthe cuff electrode, the protective structure can also be directly,preferably monolithically, connected to the carrier substrate, that iswithout the provision of a web-like connecting section.

In order to ensure that the protective structure, in the second, closedstate, cannot become loosened from the cuff electrode in an uncontrolledmanner, a preferred example of embodiment envisages a joining mechanismattached to the protective structure which, through forming at least oneof a positive and non-positive connection, secures the protectivestructure in the second, closed state. The joining mechanism ispreferably configured in the form of a locking mechanism. Velcro-typeconnection structures and at least one of a strip or thread-likefastener can also be applied to the protective structure, which throughthe formation of at least one of loops and knots ensure durable, firmholding of the protective structure on the cuff electrode.

In a preferred embodiment, the protective structure has two cylindricalhalf shells, which, mutually are at least one of complementing andoverlapping each other and enclose a straight cylindrical hollow space,in which the carrier substrate section is wrapped to form a tube and anerve bundle, around which the cuff electrode is applied, to beseamlessly housed.

The two cylindrical half shells are preferably connected to each otherin one piece, to monolithically, and preferably by way of a solid bodyjoint and are transferable from an open state into a closed state, whichenclose the cylindrical hollow space through a simple folding procedure.In the area of the directly adjoining or partially overlapping halfshell edges, at least one joining mechanism of the previously describedtype is provided, which is preferably configured in the form of alocking mechanism. Alternatively to, or in combination with the lockingmechanism, at least one strip or thread fixing means is provided, whichthrough suitable fastening openings applied within the half shells isfixable by way of at least one of forming loops and knots.

A further embodiment has a configuration of the protective structure asa film wrap-around cuff, which in each case comprises a single, flat,wrapping encompassing a cylindrical hollow space. Preferably, in thiscase the protective structure has a greater film thickness compared withthe carrier substrate thickness of the first carrier substrate sectionof the cuff electrode wrapped in a tube, especially since the protectivestructure should have as much material-inherent shape-retaining materialstiffness as possible in order to be able to exert a protectiveretaining force on the cuff electrode inside it. In this case, anadditional joining mechanism can hold the protective structure in theclosed state as a mechanical lock.

In addition to at least one of the pure fastening and holding functionas well as protection against tissue growth, a further preferredembodiment of the protective structure has electrosensor function. Thus,on its surface radially facing away from the wrap axis in its closedsecond state, the protective structure has at least one contactelectrode which is connected to an electrical conducting structureintegrated within the protective structure and extends along the secondcarrier substrate section. In this way, in the implanted state the atleast one contact electrode applied on the outer side of the protectivestructure comes into physical and electrical contact with theextravascular tissue environment, through which electrical signals canbe picked up which can be utilised for diagnostic signal recording, forexample as ECG signal tapping.

The electrodes within the cuff electrode, as well as the aforementionedat least one contact electrode attached to the surface of the protectivestructure are each contacted via electrical leads running within atleast one of the carrier substrate of the cuff electrode and theprotective structure, which all are coupled to the supply unit,preferably in the form of a control and electrical energy source unit,implanted separately to the cuff electrode.

The electrical supply and discharge structure extending between the cuffelectrode and the implantable electrical supply unit, is preferablyconnected to the carrier substrate of the cuff electrode via anelectromagnetic connecting structure, preferably in the form of a plugconnection. By way of the at least one connecting section, theprotective structure according to the invention is either connecteddirectly in one piece to the second carrier substrate section of thecuff electrode or applied with the electrical supply and dischargestructure to or as close to the electro-mechanical connection structureas possible.

Both the carrier substrate of the cuff electrode as well as thefilm-like protective structure are connected to each other in one piecein the form of a thin layer or a thin film and have thin layer or thinfilm thicknesses in the range between 5 μm and 50 μm which is preferablybetween 5 μm and 20 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

As an example, the invention will be described below, withoutrestricting the scope of the invention, by way of examples of embodimentwith reference to the drawings Here:

FIGS. 1a, b show cuff electrodes with a protective structure in the openstate a) and in the closed state b);

FIG. 2 shows cuff electrodes in accordance with the prior art;

FIGS. 3a-e show different stress states of the cuff electrode on a nervebundle;

FIGS. 4a, b show an alternative design of the cuff electrode andapplication of the protective structure;

FIGS. 5a, b show an alternative design of a protective structure in theopen state a) and in the closed state b); and

FIG. 6 shows an alternative design and application of the protectivestructure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1a shows a medical implant 1 as a wrap-around cuff electrode orcuff electrode as already presented in FIG. 2, with the carriersubstrate section 3 of the carrier substrate 2 formed by wrapping atleast one and a half, and preferable two or multiple times about thewrap axis, and through a material which inherently or a pre-determinedmaterial which is pre-tensione that assumes the shape of a tube in whichthe cuff electrode can be fixed in a self-supporting manner immovably onthe peripheral edge of a nerve. Already discussed are the components ofthe medical implant 1 with reference numbers which will not be describedagain in order to avoid repetition.

In order to mechanically protect the carrier substrate region 3 of thecuff electrode wrapped around the wrap axis 5 to form a tube, aprotective structure 8 is provided, which via a weblike connectingsection 8′, is connected to the carrier substrate 2 at the secondcarrier substrate region 6 and more particularly on the weblike surfacesection 61. The protective structure 8 as well as the weblike connectingsection 8′ are made of the same film material as the carrier substrate 2of the cuff electrode which is preferably a thin-film or thin-layer ofpolyamide film, which preferably has a film thickness in the rangebetween 5 μm and 20 μm. The connecting section 8′ and the carriersubstrate 2 are preferably monolithically connected.

The protective structure 8 comprises two cylindrical half shells 9, 10which are monolithically connected to each other, preferably by way of asolid body joint 11. The solid body joint 11 is preferably a crease.

After applying the medical implant 1 along a nerve fiber bundle, for thepurpose of mechanically protection, the protective structure 8 shown inthe open state according to FIG. 1a is transferred into the closed stateaccording to FIG. 1b , through which both half shells 9, 10 are joined,forming a straight hollow cylinder around the first carrier substrateregion 3 wrapped in a tube. The closed state of the protective structure8 shown in FIG. 1b , in which for better illustration both half-shells9, 10 are each shown transparently, indicates that the hollowcylinder-shaped closed form of the protective structure 8 completelyencloses the wrap-around cuff contained therein both in the peripheraldirection and also axially to the wrap axis 5. In the closed state, theprotective structure 8 preferably has an axial excess portion on eachside facing the wrap-around cuff, so that that the internally arrangedwrap-around cuff is prevented from being functionally impaired by tissuegrowth.

Both half shells 9, 10 of the protective structure 8 are joined togetheras a complete straight hollow cylinder, which can advantageously be heldpermanently in the closed state by a joining mechanism 12 which is onlyshown schematically.

WA As an alternative to applying the web connection section 8′ directlyto the surface section 61, it is also possible, to connect the web-likeconnecting structure 8″ indicated with the dashed line in FIG. 1 b, sothat the connecting structure 8″ leads away from the implant 1,preferably in the immediate vicinity of the interface S.

FIGS. 4a and b show an alternative embodiment of the medical implant asthe cuff electrode 1 which largely comprises a carrier substrate region3 wrapped to form a tube, from which a surface section of the carriersubstrate leads off directly, along which the electrical leads 7, (notshown in detail,) lead off. The protective structure 8, which like theembodiment in FIGS. 1a, b comprises two half shells 9, 10, whichdirectly adjoins the carrier substrate region 3 without any connectingstructure. In FIG. 4b , the closed state of the protective structure 8is illustrated. To facilitate better understanding, the protectivestructure 8 is shown transparently. In this form of embodiment, the endedges of the half shells 9, 10 overlap along an overlap Ü.

In FIG. 5a , an alternative design of the protective structure 8 isshown. In this case, the protective structure 8 is a film-like surfacesection into which are material inherently or mechanically pre-tensionedis introduced so that the protective structure 8 can only be held in theopen state as shown in FIG. 5a when an external force F is applied. Likethe protective structure 8 illustrated in FIG. 1a , the flatlyconfigured protective structure 8 is monolithically connected to thesecond carrier substrate region 6, particularly at the surface section61 by way of a weblike connecting section 8′.

After application of the cuff electrode to the nerve bundle, theprotective structure 8 is transferred into the closed state according toFIG. 5b , wherein the surface section of the protective structure 8reshapes itself as a result of the inherent mechanical pre-tensioning toform a straight hollow cylinder. The holding force, through which theprotective structure 8 is kept in the closed state, can preferably beincreased in that the thickness of the surface section of the protectivestructure 8 is selected to be correspondingly greater, for examplelarger than the film thickness in the area of the carrier substrate 2.

As has already been mentioned, measures regarding the an additionaljoining mechanism as well as an alternative application of theprotective structure 8 with the connecting structure 8′ without theconnecting structure, that is by direct application of the protectivestructure 8 to the carrier substrate region 3, is comparable with theembodiment of the cuff electrode in accordance with FIGS. 4a, b , whichcan be used in the case of the example of embodiment shown in FIG. 5 andb.

FIG. 6 shows a protective structure 8 in the closed state, which 8encloses the cuff electrode situated within it. Protective structure 8can be two half shells, as shown in FIGS. 1a, b , or as a wrap-aroundcuff as shown in FIGS. 5a, b . In contrast to the illustrated forms ofembodiment, in this case the protective structure 8 is connected via aconnecting structure 8″ with a sheathing 13 made of elastomer material,preferably of silicone or a silicone-based plastic, which surrounds atleast one section of the surface section 61. The preferably tubularsheathing 8 is joined in a positive manner to the film-like surfacesection 61 by way of an anchoring structure 14 applied in one piece tothe surface section 61. The surface section 61 is part of the carriersubstrate 2 and directly or indirectly adjoins the carrier substrateregion 3 of the cuff electrode wound to form a tube. The shape and sizeof the sheathing 13 are selected for the purpose of intracorporealapplication to a nerve fiber bundle, is made easier for a doctor tohandle. Not necessarily, but advantageously, the protective structure 8is made of the same material from which the sheathing 13 is made.

LIST OF REFERENCE NUMBERS

-   1 Medical implant-   2 Carrier substrate-   3 First carrier substrate region-   4 Free section end-   5 Wrap axis-   6 Second carrier substrate region-   61 Weblike surface section-   7 Connecting structure-   8 Protective structure-   8′, 8″, 8′″ Connecting section-   9, 10 Half shells-   11 Solid body joint-   12 Joining mechanism-   13 Sheathing-   14 Anchoring structure-   Ü Overlap

1-16: (canceled)
 17. A medical implant formed as a wrap-around cuffelectrode assembly, comprising a flexible, biocompatible, film carriersubstrate, including a carrier substrate which upon wrapping forms atube, a protective structure applied to the carrier substrate, which isconfigurable from a first, open state into a second, closed state whichaxially encloses at parts of the carrier substrate region and completelyencloses a peripheral direction of the tube.
 18. The medical implantaccording to claim 17, wherein the structure of the substrate is film.19. The medical implant according to claim 17, wherein the protectivestructure closed second state completely covers the carrier substrate ofthe cuff electrode wound to form a tube axially and in the peripheraldirection of the tube.
 20. The medical implant according to claim 18,wherein the protective structure closed second state completely coversthe carrier substrate of the cuff electrode wound to form a tube axiallyand in the peripheral direction of the tube.
 21. The medical implantaccording claim 17, wherein a joining mechanism is on the protectivestructure which is detachably and secures the protective structure inthe second closed state.
 22. The medical implant according claim 18,wherein a joining mechanism is on the protective structure which isdetachably and secures the protective structure in the second closedstate.
 23. The medical implant according claim 19, wherein a joiningmechanism is on the protective structure which is detachably and securesthe protective structure in the second closed state.
 24. The medicalimplant according to claim 17, wherein the protective structure isconnected by at least one web connecting section to the carriersubstrate.
 25. The medical implant according to claim 18, wherein theprotective structure is connected by at least one web connecting sectionto the carrier substrate.
 26. The medical implant according to claim 19,wherein the protective structure is connected by at least one webconnecting section to the carrier substrate.
 27. The medical implantaccording to claim 21, wherein the protective structure is connected byat least one web connecting section to the carrier substrate.
 28. Themedical implant according to claim 17, wherein the protective structureis two cylindrical half shells which are mutually complementing to eachother and enclose a straight cylindrical hollow space.
 29. The medicalimplant according to claim 18, wherein the protective structure is twocylindrical half shells which are mutually complementing to each otherand enclose a straight cylindrical hollow space.
 30. The medical implantaccording to claim 19, wherein the protective structure is twocylindrical half shells which are mutually complementing to each otherand enclose a straight cylindrical hollow space.
 31. The medical implantaccording to claim 21, wherein the protective structure is twocylindrical half shells which are mutually complementing to each otherand enclose a straight cylindrical hollow space.
 32. The medical implantaccording to claim 24, wherein the protective structure is twocylindrical half shells which are mutually complementing to each otherand enclose a straight cylindrical hollow space.
 33. The medical implantaccording to claim 28, wherein the two cylindrical half shells areconnected to each other by a solid joint and can be changed from an openstate into a closed second state enclosing the cylindrical hollow space.34. The medical implant according to claim 17, wherein the protectivestructure is wrap around film cuff, which comprises a flat wrapenclosing a cylindrical hollow space.
 35. The medical implant accordingto claim 17, wherein the protective structure in the closed second statehas a surface radially facing away from the wrap axis on which at leastone contact electrode is applied which is connected with an electricalconducting structure integrated within the protective structure andextending along the carrier substrate.
 36. The medical implant accordingto claim 35, wherein the carrier substrate region is one piece wrappedto form a tube which is a second carrier substrate region along which anelectromechanical connecting structure is applied, to which anelectrical supply and discharge structure is attached that extends to animplantable electrical supply unit, and the protective structure isattached to the electrical supply and discharge structure.
 37. Themedical implant according to claim 36, wherein the second carriersubstrate region is surrounded at least in sections by a sheathing of anelastic material.
 38. The medical implant according to claim 37, whereinthe protective structure is connected in one piece to the sheathing. 39.The medical implant according to claim 17, wherein the protectivestructure is connected in one piece to the carrier substrate.
 40. Themedical implant according to claim 17, wherein in a first carriersubstrate region, a pre-tensioning material is the carrier substratethrough which, without an external force, assumes a predefined wrappingconfiguration in which a free section end of the carrier substrateregion is radially covered thereby in at least one layer, by a wrappingof at least one substrate.
 41. The medical implant according to claim18, wherein the carrier substrate and the protective structure are eacha layer film, and have a thickness of 5 μm to 50 μm.
 42. The medicalimplant according to claim 17, wherein the carrier substrate region is aflexible, bio-compatible, carrier substrate, which assumes a shape of atube by wrapping around an axis.